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How Obesity Affects Your Brain

November 16, 2016

Being overweight could age your brain by at least 10 years.

As you age, your brain gradually ages with you. Older brains have less white matter, the tissue and neurons that transmit information. This process, known as neurodegeneration, happens gradually and often follows a predictable pattern from middle age onward.

However, researchers at Cambridge University recently found that these changes are exacerbated in the brains of obese people. The white matter in the brain of an overweight 50-year-old, they discovered, resembled that in the brain of a 60-year-old of average weight.

Obesity, it turns out, might cause your brain to age more rapidly than it otherwise would.

The study looked at the brains of 527 people between the ages of 20 and 87. Based on their body mass index (BMI), the participants were categorized as lean or overweight. Researchers then measured the volume of white matter in their brains, along with other indicators of neurodegeneration, such as surface area.

Beginning in middle age, the study showed, the brains of overweight participants showed levels of neurodegeneration similar to lean individuals about a decade older. In other words, their brains had aged an extra 10 years compared to people of the same age with a lower weight.

The study comes as global rates of obesity are rising, leaving leaders in the health and medical fields concerned that parts of the world are facing an obesity epidemic.

According to the World Health Organization (WHO), worldwide obesity has more than doubled since 1980. In 2014, 39 percent of adults were overweight, and 13 percent were considered obese. In the United States, the National Institutes of Health reports that two-thirds of adults are considered overweight, while more than one in three are obese.

Adults aren’t the only ones at risk; the WHO also reports that in 2014 more than 40 million children around the world were considered overweight or obese. This problem isn’t confined to wealthy or developed countries. Obesity rates are rising in the developing world as well, particularly in low-income urban areas.

But researchers have only recently begun to investigate whether weight can also affect the way the brain functions in otherwise healthy adults.

The Cambridge study is not the first to look at the effects of weight on brain degeneration. A similar study was led by several of the same scientists and looked at grey matter in the brain. They found that participants with higher BMIs had thinner regions of grey matter, the parts of the brain responsible for muscle and impulse control, as well as emotional memory, decision making, and reward valuation.

In both these studies, however, researchers stress that they do not know which direction the relationship goes. Does being overweight or obese cause early neurodegeneration? Or do lower levels of grey and white matter in the brain make a person more likely to have a higher weight?

They were also unable to say whether this process would be reversible with weight loss or if neurodegeneration in overweight individuals is permanent.

Though more research is needed to fully understand how weight and brain function interact, the Cambridge study’s authors are confident that there is a connection between the two. “These results,” they write in their conclusion, “support the hypothesis that adiposity confers a significant risk of neurodegeneration and cognitive decline.”